They are Magpul XTM rail covers. I have them as well. I really like them myself.

They come 8 pieces per pack which equals 4 panels when put together. As you can see from the picture it takes 5 panels to cover a full side of the 15-22 rails. So take that into consideration if you order some. Adjust as needed for the accessories on your gun.

You can buy them directly from Magpul if you'd like or if you prefer, most of the major shooting supplies/tactical gear retailers have them... otherwise just do a Google search on them.